Application of prestressed CFRP plates to improve the flexural capacity of full size box girders for bridge

With the growing prevalence of heavy-duty vehicles, highway bridges now subjected to service loads exceeding their original design load ratings. This discrepancy not only affects the service condition of highway bridges but also accelerate the deterioration of the bridge, leading the bridge to the need for reconstruction or repair to increase its rated load capacity. Consequently, bridge strengthening becomes imperative. In contrast to the traditional methods of enlarging sections or paste steel plates, prestressed carbon fiber reinforced polymer (CFRP) plates are used to strengthen bridges and improve cracking moment and flexural capacity without significantly increasing structural weight or reducing vertical clearance. Two full-scale prestressed concrete box girders with a total length of 25 m from a bridge requiring higher load ratings were selected as test specimens. A theoretical analysis of the two girders was conducted, and their mechanical behavior was evaluated through numerical simulation and flexural destructive testing. The results demonstrated that the strengthening increased the actual cracking moment and ultimate flexural capacity of the girder by 12.6 % and 13.6 % respectively. The ratio of ultimate load stress to allowable stress of the strengthened girder under a higher vehicle load rating was close to that of the unstrengthened girder under the original vehicle load rating, Which proved that prestressed CFRP plate strengthening effectively meets the requirements for increasing the vehicle load rating of the girder.